In portable terminals such as a notebook type computer or a smartphone, a technique of suppressing power consumption in order to maintain driving using a battery has been developed. Power consumed by a portable terminal includes power consumption of a processor that performs data creation of an image to be displayed on a display. For example, when an application software running on a smartphone updates an image on a display, a processor included in the smartphone performs a process of creating new image data. Then, the processor displays a new image on the display based on the created image data. The updating of the image is performed in synchronization with synchronization signals, such as vertical synchronization signals, which are generated at predetermined time intervals.
A technique of suppressing power consumption of a processor that creates image data to be updated in synchronization with a synchronization signal includes a technique of switching an operation mode of a processor to a low power consumption mode when a process of creating image data to be performed is completed before the next synchronization signal is sent. Thereby, it is possible to reduce power consumption during a period until the next synchronization signal is sent (for example, see Japanese Laid-open Patent Publication No. 2005-62798).
Japanese Laid-open Patent Publication No. 2005-62798 discloses that the processor is shifted to a power saving mode when the processing of image data to be processed within a unit rendering period is completed prior to the completion of the unit rendering period. However, Japanese Laid-open Patent Publication No. 2005-62798 mentioned above does not disclose a specific method of recognizing that the processing of image data to be processed is completed. Therefore, it may not be said that the method disclosed in Japanese Laid-open Patent Publication No. 2005-62798 has sufficient convenience as a technique of suppressing power consumption.